Anti-clockwise reduces power of the dehumidifier, so lower high humidity. Vice versa. Mine at around 12 o'clock, after months of tweaking. I think the exact position depends cabinet, room, location, etc.
I've been using this for almost 2 years and it's working fine. You just need to fine tune the RH level in the beginning, thereafter you won't need to touch it anymore.
meanwhile, allow me to bitch abt having to fine tune the knob. i reckon it'll take at least 1 week to get the correct knob position. have been setting the knob and monitoring, then re-set and monitor, set and monitor................................................... :sweat: